Methods and Materials for the Functionalization of Polymers and Coatings Including Functionalized Polymer

ABSTRACT

The disclosure provides a functionalized polymer for use in coating compositions and a method for making the functionalized polymer. In some embodiments, the functionalized polymer is a water-dispersible polymer, more preferably a water-dispersible polyester polymer, having one or more side groups including one or more salt groups. Packaging containers (e.g., food or beverage cans) comprising the functionalized polymer and methods of making such containers are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/968,981 (now U.S. Pat. No. ______), filed Aug. 16, 2013, which is acontinuation-in-part of International Application No. PCT/US2013/026322filed on Feb. 15, 2013, which claims the benefit of U.S. ProvisionalApplication No. 61/600,430 filed on Feb. 17, 2012, each of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to the field of polymers. Morespecifically, the present disclosure relates to the field of polymersfor use in coating compositions, including, for example, packagingcoatings for use on packaging cans and containers.

BACKGROUND

A wide variety of coatings have been used to coat the surfaces of foodand beverage cans. The cans are often coated using “coil coating”operations, i.e., a planar sheet of a suitable metal substrate (e.g.,steel or aluminum metal) is coated with a suitable composition and curedand then the coated substrate is formed into the can end or body. Thecoating should preferably be capable of high-speed application to thesubstrate and provide the necessary properties when cured to perform inthis demanding end use. For example, the coating should preferably besafe for prolonged food contact; have excellent adhesion to thesubstrate; be capable of being drawn during the forming step; when usedas a can end coating, provide clean edges when the can end is opened toaccess the packaged product; resist staining and other coating defectssuch as “popping,” “blushing” and/or “blistering;” and resistdegradation over long periods of time, even when exposed to harshenvironments. Previous coatings have suffered from one or moredeficiencies.

Various coatings have been used as interior protective can coatings,including epoxy-based coatings and polyvinyl-chloride-based coatings.Each of these coating types, however, has potential shortcomings. Forexample, the recycling of materials containing polyvinyl chloride orrelated halogen-containing vinyl polymers can be problematic. There isalso a desire by some to reduce or eliminate certain epoxy compoundscommonly used to formulate food-contact epoxy coatings.

To address the aforementioned shortcomings, the packaging coatingsindustry has sought coatings based on alternative binder systems such aspolyester resin systems. It has been problematic, however, to formulatepolyester-based coatings that exhibit the required balance of coatingcharacteristics (e.g., flexibility, adhesion, corrosion resistance,stability, resistance to crazing, etc.). For example, there hastypically been a tradeoff between corrosion resistance and fabricationproperties for such coatings. Polyester-based coatings suitable forfood-contact that have exhibited both good fabrication properties and anabsence of crazing have tended to be too soft and exhibit unsuitablecorrosion resistance. Conversely, polyester-based coatings suitable forfood contact that have exhibited good corrosion resistance havetypically exhibited poor flexibility and unsuitable crazing whenfabricated.

What is needed in the marketplace is an improved binder system for usein coatings such as, for example, packaging coatings. Such packages,compositions and methods for preparing the same are disclosed andclaimed herein.

SUMMARY

In one aspect, the present disclosure provides a functionalized polymerhaving one or more functional groups preferably located at one or more“intermediate” locations of the polymer (e.g., locations other than theterminal end of a backbone of the polymer). The functionalized polymerpreferably includes one or more side groups having one or morefunctional groups. The side group can be attached at any suitablelocation including, for example, directly to a backbone of the polymeror to another portion of the polymer (e.g., attached to a pendant groupthat is in turn attached to a backbone of the polymer). In preferredembodiments, the functional-group-containing side group is derived froman unsaturated compound having one or more functional groups. Thefunctional-group-containing side group is preferably incorporated intothe polymer and/or a precursor thereof via a reaction that does notrequire a free-radical polymerization initiator.

The backbone of the functionalized polymer typically includes one ormore heteroatoms. In certain preferred embodiments, the backbone is apolyester backbone.

In some embodiments, the functionalized polymer is a water-dispersiblepolymer such as, for example, a water-dispersible polyester polymer. Thewater-dispersible polymer preferably includes one or more side groupshaving one or more functional groups in the form of a salt group suchas, e.g., a neutralized acid or base group.

In another aspect, the present disclosure provides a polymer having oneor more functional-group-containing structural units (e.g., side groups)that are the reaction product of a pericylic reaction (e.g., a pericylicEne reaction or a cycloaddition reaction such as a Diels-Alder reaction)or a non-pericyclic Ene reaction. The structural unit may be located atany suitable location, including, for example, in pendant locations orterminal backbone locations. In some embodiments, thefunctional-group-containing structural unit is a pericyclic reactionproduct, more preferably a Diels-Alder or Ene reaction product, of anunsaturated compound having one or more functional groups, morepreferably one or more functional groups described herein (e.g., a saltor salt-forming group). In an embodiment, the unsaturated compound, theresulting functional-group-containing structural unit of the polymer, ormore preferably both of the aforementioned, has an atomic weight of lessthan about 200 Daltons.

In yet another aspect, the present disclosure provides a method forproducing a functionalized polymer. The method includes providing anunsaturated polymer or prepolymer having one or more double or triplebonds, more typically one or more carbon-carbon double or triple bonds.In some embodiments, an unsaturated polymer is provided that is a linearor substantially linear condensation and/or step-growth polymerpreferably having a number average molecular weight of greater than2,000, and more preferably greater than 4,000. An unsaturated compoundhaving one or more desired functional groups is then reacted with theunsaturated polymer or prepolymer to attach one or morefunctional-group-containing side groups. The side group is preferablyattached via a reaction involving one or more double or triple bonds ofthe polymer or prepolymer and one or more double or triple bonds of theunsaturated compound. In some embodiments, the side group is attached toa backbone, or other portion, of the polymer via one or morecarbon-carbon bonds. In preferred embodiments, the one or more covalentattachments are formed between the unsaturated compound and theunsaturated polymer or prepolymer using a Diels-Alder reaction, an Enereaction, or both Diels-Alder and Ene reactions.

In yet another aspect, the present disclosure provides a coatingcomposition including a functionalized polymer of the presentdisclosure. The coating composition preferably includes at least afilm-forming amount of the polymer. In some embodiments, the coatingcomposition is a water-based coating composition that may be applied,for example, as an adherent coating for articles such as, e.g.,packaging articles (e.g., light metal packaging articles such as food orbeverage containers, cosmetic containers, drug containers, portions ofany of these, etc.).

The present disclosure also provides packaging articles having a coatingcomposition of the present disclosure disposed on a surface thereof,which is typically a metal surface. In one embodiment, the packagingarticle is a container such as a food or beverage container, or aportion thereof (e.g., a twist-off closure lid, beverage can end, foodcan end, etc.), wherein at least a portion of an interior surface of thecontainer (e.g., a food or beverage product facing side of thecontainer) is coated with a coating composition described herein that issuitable for prolonged contact with a food or beverage product or otherpackaged product.

In one embodiment, a method of preparing a container is provided thatincludes an interior, food-contact coating of the present disclosure.The method includes: providing a coating composition described hereinand applying the coating composition to at least a portion of a surfaceof a substrate prior to or after forming the substrate into a containeror a portion thereof having the coating composition disposed on aninterior and/or exterior surface. Typically, the substrate is a metalsubstrate, although the coating composition may be used to coat othersubstrate materials if desired.

In another embodiment, a method of forming a food or beverage can end(e.g., a riveted can end such as a riveted beverage can end for a beer,soda, or juice can) is provided that includes: applying a water-basedcoating composition including a water-dispersible polyester polymerdescribed herein on a metal substrate (e.g., aluminum or steel) in theform of a planar coil or sheet, hardening the coating composition, andforming the planar coil or sheet into a food or beverage can end.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation. The description thatfollows more particularly exemplifies illustrative embodiments. Inseveral places throughout the application, guidance is provided throughlists of examples, which examples can be used in various combinations.In each instance, the recited list serves only as a representative groupand should not be interpreted as an exclusive list.

The details of one or more embodiments of the disclosure are set forthin the description below. Other features, objects, and advantages of theinvention will be apparent from the description and from the claims.

Selected Definitions

Unless otherwise specified, the following terms as used herein have themeanings provided below.

As used herein, the term “organic group” means a hydrocarbon group (withoptional elements other than carbon and hydrogen, such as oxygen,nitrogen, sulfur, and silicon) that is classified as an aliphatic group,cyclic group, or combination of aliphatic and cyclic groups (e.g.,alkaryl and aralkyl groups). The term “aliphatic group” means asaturated or unsaturated linear or branched hydrocarbon group. This termis used to encompass alkyl, alkenyl, and alkynyl groups, for example.The term “alkyl group” means a saturated linear or branched hydrocarbongroup including, for example, methyl, ethyl, isopropyl, t-butyl, heptyl,dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term “alkenylgroup” means an unsaturated, linear or branched hydrocarbon group withone or more carbon-carbon double bonds, such as a vinyl group. The term“alkynyl group” means an unsaturated, linear or branched hydrocarbongroup with one or more carbon-carbon triple bonds. The term “cyclicgroup” means a closed ring hydrocarbon group that is classified as analicyclic group or an aromatic group, both of which can includeheteroatoms. The term cycloaliphatic group means an organic group thatcontains a ring that is not an aromatic group.

A group that may be the same or different is referred to as being“independently” something. Substitution is anticipated on the organicgroups of the compounds of the present disclosure. As a means ofsimplifying the discussion and recitation of certain terminology usedthroughout this application, the terms “group” and “moiety” are used todifferentiate between chemical species that allow for substitution orthat may be substituted and those that do not allow or may not be sosubstituted. Thus, when the term “group” is used to describe a chemicalsubstituent, the described chemical material includes the unsubstitutedgroup and that group with O, N, Si, or S atoms, for example, in thechain (as in an alkoxy group) as well as carbonyl groups or otherconventional substitution. Where the term “moiety” is used to describe achemical compound or substituent, only an unsubstituted chemicalmaterial is intended to be included. For example, the phrase “alkylgroup” is intended to include not only pure open chain saturatedhydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl,and the like, but also alkyl substituents bearing further substituentsknown in the art, such as hydroxy, alkoxy, alkylsulfonyl, halogen atoms,cyano, nitro, amino, carboxyl, etc. Thus, “alkyl group” includes ethergroups, haloalkyls, nitroalkyls, carboxyalkyls, hydroxyalkyls,sulfoalkyls, etc. On the other hand, the phrase “alkyl moiety” islimited to the inclusion of only pure open chain saturated hydrocarbonalkyl substituents, such as methyl, ethyl, propyl, t-butyl, and thelike. As used herein, the term “group” is intended to be a recitation ofboth the particular moiety, as well as a recitation of the broader classof substituted and unsubstituted structures that encompasses the moiety.

The term “double bond” refers to any type of double bond between anysuitable atoms (e.g., C, O, N, etc.), but excludes aromatic doublebonds.

The term “triple bond” is non-limiting and refers to any type of triplebond between any suitable atoms.

The terms “unsaturated” or “unsaturation” when used in the context of amaterial or group refers to a material or group that includes at leastone non-aromatic double bond or triple bond, more typically anon-aromatic carbon-carbon double bond.

The term “substantially free” of a particular mobile compound means thatthe compositions of the present disclosure contain less than 100 partsper million (ppm) of the recited mobile compound. The term “essentiallyfree” of a particular mobile compound means that the compositions of thepresent disclosure contain less than 10 ppm of the recited mobilecompound. The term “essentially completely free” of a particular mobilecompound means that the compositions of the present disclosure containless than 1 ppm of the recited mobile compound. The term “completelyfree” of a particular mobile compound means that the compositions of thepresent disclosure contain less than 20 parts per billion (ppb) of therecited mobile compound.

The term “mobile” means that the compound can be extracted from thecured coating when a coating (typically ˜1 mg/cm² (6.5 mg/in²) thick) isexposed to a test medium for some defined set of conditions, dependingon the end use. An example of these testing conditions is exposure ofthe cured coating to HPLC-grade acetonitrile for 24 hours at 25° C. Ifthe aforementioned phrases are used without the term “mobile” (e.g.,“substantially free of XYZ compound”) then the compositions of thepresent disclosure contain less than the aforementioned amount of thecompound whether the compound is mobile in the coating or bound to aconstituent of the coating. If the aforementioned phrases are usedwithout the term “mobile” (e.g., “substantially free of XYZ compound”)then the compositions of the present disclosure contain less than theaforementioned amount of the compound whether the compound is mobile inthe coating or bound to a constituent of the coating.

The term “crosslinker” refers to a molecule capable of forming acovalent linkage between polymers or between two different regions ofthe same polymer.

The term “water-dispersible” in the context of a water-dispersiblepolymer means that the polymer can be mixed into water (or an aqueouscarrier) to form a stable mixture. For example, a mixture that separatesinto different layers after being stored for 12 hours at 21° C. undernormal storage conditions is not a stable mixture. The term“water-dispersible” is intended to include the term “water-soluble.” Inother words, by definition, a water-soluble polymer is also consideredto be a water-dispersible polymer.

The term “dispersion” in the context of a dispersible polymer refers tothe mixture of a dispersible polymer and a carrier. The term“dispersion” is intended to include the term “solution.”

Unless otherwise indicated, a reference to a “(meth)acrylate” compound(where “meth” is bracketed) is meant to include both acrylate andmethacrylate compounds.

The term “on,” when used in the context of a coating applied on asurface or substrate, includes both coatings applied directly orindirectly to the surface or substrate. Thus, for example, a coatingapplied to a primer layer overlying a substrate constitutes a coatingapplied on the substrate.

Unless otherwise indicated, the term “polymer” includes bothhomopolymers and copolymers (i.e., polymers of two or more differentmonomers). Thus, for example, the term “polyester polymer” includescopolyesters.

The term “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

The terms “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances.

Furthermore, the recitation of one or more preferred embodiments doesnot imply that other embodiments are not useful, and is not intended toexclude other embodiments from the scope of the disclosure.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a coating composition thatcomprises “an” additive can be interpreted to mean that the coatingcomposition includes “one or more” additives.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.). Furthermore, disclosure of a range includesdisclosure of all subranges included within the broader range (e.g., 1to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).

DETAILED DESCRIPTION

In one aspect, the present disclosure provides materials and methods forfunctionalizing a polymer to include one or more functional groups. Inpreferred embodiments, the functionalization is performed on a preformedunsaturated polymer. The functionalization process typically consumes atleast one double or triple bond of the unsaturated polymer. Afterfunctionalization, the molecular weight of the functionalized polymermay optionally be increased if desired. Alternatively, an unsaturatedprepolymer (e.g., an oligomer or low-molecular-weight polymer) may befunctionalized and upgraded to the desired final molecular weight afterfunctionalization. The final functionalized polymer will typically beunsaturated, but it may be optionally modified (e.g., via hydrogenation)to yield a saturated polymer.

The added functionality may confer one or more benefits to the polymersuch as, for example, providing sites for crosslinking, facilitatingdispersal of the polymer into an aqueous medium, improving thecompatibility of the polymer with one or more other materials, improvingadhesion of the cured coating to substrate, and so on. The one or moreadded functional groups may be present at any suitable location,including for, example, at terminal backbone locations, at pendantgroups locations (e.g., present in a side group attached directly to thepolymer backbone or in a side group that is separated from the polymerbackbone by one or more branch points), and combinations thereof.

In preferred embodiments, the functionalized polymer includes a backbonehaving one or more heteroatoms. Preferred such backbones includecondensation backbones and/or step-growth backbones. Such backbones mayinclude any combination of condensation and/or step growth linkages,including, for example, amide, carbonate ester, ester, ether, imide,urea, urethane, or combinations thereof. In certain preferredembodiments, the polymer has a polyester backbone that may optionallyinclude any other suitable linkages. Thus, for example, in someembodiments, the polyester polymer may be a polyester-urethane polymer.

The functionalized polymer preferably includes at least one functionalgroup present in a side group that is attached to the backbone oranother portion of the polymer (e.g., another portion attached to thebackbone). In some embodiments, the side group constitutes an entirependant group attached directly to the backbone, whereas in otherembodiments the side group constitutes a portion of a pendant group andthe side group itself is not directly attached to the backbone. Inpreferred embodiments, the functional-group-containing side group isattached to another portion of the polymer via one or more carbon-carbonbonds, more typically one or more carbon-carbon single bonds.

In some embodiments, a side group is located at one or both ends of thebackbone. For example, one or both terminal ends of a preformed polymermay be modified to include a carbon-carbon double bond which issubsequently reacted with the unsaturated compound via a reactiondisclosed herein to incorporate a functional-group-containing side groupat one or both terminal ends of the backbone.

In preferred embodiments, the one or more functional-group-containingside groups are derived from an unsaturated compound, which typicallyincludes one or more carbon-carbon double or triple bonds, moretypically one or more carbon-carbon double bonds. A pericyclic reactionis preferably used to incorporate the unsaturated compound into thepolymer or a precursor thereof. Suitable pericyclic reactions includeEne reactions and cycloaddition reactions. A Diels-Alder reaction is apreferred cycloaddition reaction. The resulting side group is typicallyunsaturated, although the side group may optionally be saturated.

While it is contemplated that polymers of the present disclosure mayinclude side groups that are free-radical-polymerized vinyl and/oracrylic groups, presently preferred side groups derived from theunsaturated compound are not free-radical-polymerized. Thus, preferredfunctional-group-containing side groups are incorporated into thepolymer in a reaction that does not involve a free-radical initiator.Examples of free-radical-polymerized groups include vinyl groups (alsosometimes referred to as “acrylic” groups when (meth)acrylates and/or(meth)acrylic acids are used) formed via free-radical-initiated reactionof ethylenically unsaturated monomers such as alkyl acrylates (e.g.,ethyl acrylate, propyl acrylate, butyl acrylate, hydroxyl propylacrylate, hydroxy butyl acrylate, glycidyl acrylate, etc.), alkylmethacrylates (e.g., ethyl methacrylate, methyl methacrylate, propylmethacrylate, butyl methacrylate, hydroxypropyl methacrylate,hydroxybutyl methacrylate, glycidyl methacrylate, etc.), acrylic acid,methacrylic acid, vinyl aromatics (e.g., styrene, vinyl toluene, etc.),vinyl chloride, acrylamides, methacrylamides, acrylonitriles, vinylacetate, and the like, and combinations thereof. Examples offree-radical initiators include thermal free-radical initiators,photochemical free-radical initiators, and the like. Examples of thermalfree-radical initiators include peroxide initiators, redox initiatorsystems, persulfate initiators, azoalkane initiators, and the like.

For example, acid-functional acrylic groups are sometimes incorporatedinto polymers such as polyester polymers to render the polymerdispersible in water (see, e.g., U.S. Pub. No 2005/0196629 for adiscussion of such water-dispersible polyester-acrylic graftcopolymers). The acid-functional acrylic groups are typicallyincorporated into the polymer via reaction with a carbon-carbon doublebond of the polymer via a free-radical polymerization reaction involvinginitiator.

While certain Ene reactions may involve free-radical reactions, itshould be noted that such reactions do not involve free-radicalinitiators such as are employed for free-radical-polymerized vinylgroups.

In some embodiments, the side group includes a functional group locatedat a terminal end of the side group away from the portion of the sidegroup attached to the backbone or other portion of the polymer. Afunctional group of the side group may be attached to the backbone orother portion of the polymer via a branched or un-branched, saturated orunsaturated carbon chain that does not include any heteroatoms in thechain. An example of such a carbon chain is the structure—(C(R¹)_(m))_(n)—, wherein: each R¹ is independently any suitable atomor group (e.g., a hydrogen atom, a halogen atom, an organic group,etc.); each m is independently 0, 1, or 2; n denotes an integerpreferably from 1 to 20, more preferably from 1 to 10; and one or moreR¹ may optionally join together with one or more other R¹ and/or withanother portion or portions of the polymer.

In some embodiments, the side group does not include any repeat units.In preferred such embodiments, the side group is attached directly tothe backbone, or a pendant group that is attached to the backbone, andis derived from a single molecule of the unsaturated compound (e.g., asingle molecule of sorbic acid or the like). This approach can result ina functional-group-containing side group (e.g., when sorbic acid or thelike is used as the unsaturated compound) that does not crosslink withdouble or triple bonds present in other polymer strands or free monomer.This is distinct, e.g., from the acrylate groups of polyester-acrylatecopolymers.

The functionalized polymer may have utility in a variety of end uses,including as an ingredient of a coating composition. The functionalizedpolymer is particularly useful as a binder polymer of an adherentcoating composition. Coating compositions of the present disclosure mayoptionally include one or more of additional ingredients such as, forexample, a liquid carrier, a crosslinker, a pigment, a lubricant, acatalyst, etc. The coating composition may be a powder coatingcomposition or extrusion coating composition in certain embodiments.Typically, however, the coating composition is applied to a substratewith the assistance of a liquid carrier.

A benefit of the method of the present disclosure is that it allows forthe addition of one or more functional groups to a polymer at one ormore “intermediate” locations (e.g., locations other than terminalbackbone locations such as pendant locations) after the polymer has beenformed or substantially formed, which can eliminate the need to usecertain tri-functional or higher reactants to provide such functionalgroups. The use of certain tri-functional or higher reactants, such as,for example, reactants having three of more of the same type of activehydrogen group (e.g., triols or tricarboxylic acids), can lead tounsuitably high levels of branching, and even gelling, before thedesired molecular weight and/or degree of functionalization is achieved.While it may be possible to use such tri-functional or higher reactantsin relatively low concentrations while avoiding gellation of the sample,it may not be possible to achieve the desired molecular weight anddegree of functionalization at such concentrations. Thus, in someembodiments, the method of the present disclosure enables the productionof a substantially linear polymer having a molecular weight and a degreeof functionalization that is not typically achievable using conventionalcondensation polymerization techniques—particularly when the desiredfunctional groups are reactive with other functional groups present inthe polymerization mixture. Examples of substantially linear polymersinclude polymers in which substantially all (e.g., >95 wt-%, >98wt-%, >99 wt-%, >99.5 wt-%, etc.) of the monomers used to form thepolymer are di-functional or mono-functional monomers. Accordingly,substantially linear polymers typically include less than 5 weightpercent (“wt-%”), less than 2 wt-%, less than 1 wt-%, or less than 0.5wt-% of tri-functional or higher monomers.

For example, in some embodiments, the method of the present disclosurecan be used to produce a substantially linear functionalizedcondensation and/or step-growth polymer such as, for example, asubstantially linear functionalized polyester polymer having functionalgroup(s) (e.g., active hydrogen groups) at one or more intermediatelocation and a molecular weight greater than 4,000 number averagemolecular weight (“Mn”). In some such embodiments (e.g., in which a meltpolymerization process is used,), the method can be used to produce sucha higher molecular weight polymer (e.g., a polyester polymer) having,for example, a Mn of at least about 10,000 and more preferably fromabout 10,000 to about 30,000.

In preferred embodiments, the method of the present disclosure includesproviding an unsaturated precursor polymer or prepolymer having one ormore double or triple bonds. Although branched materials may be used,the unsaturated polymer or prepolymer is typically linear orsubstantially linear. (For purposes of convenience, the unsaturatedpolymer or prepolymer thereof having one or more double or triple bondswill be referred to collectively hereinafter as the “unsaturatedprecursor polymer,” or when used in the context of a polyester polymer,as the “unsaturated polyester precursor polymer.”) While the one or moredouble or triple bonds of the unsaturated precursor polymer aretypically located in a backbone of the polymer, the double or triplebonds may also be located in one or more pendant groups.

The unsaturated precursor polymer is preferably reacted with anunsaturated compound having the desired functionality. Typically, thereaction results in a thermal adduct of the unsaturated compound of theunsaturated precursor polymer, but it is also contemplated that othersuitable reaction mechanisms may be used. In preferred embodiments, thereaction is performed at an elevated temperature such as, for example,from about 140° C. to about 220° C., more preferably from about 160° C.to about 200° C., and even more preferably from about 170° C. to about190° C.

Preferably, the unsaturated compound includes both: (i) one or moredouble bonds, more typically one or more carbon-carbon double bonds and(ii) one or more desired functional groups (which are typically groupsother than double or triple bonds). Examples of suitable such functionalgroups may include active hydrogen groups having a hydrogen attached to,e.g., an oxygen (O), sulfur (S), and/or nitrogen (N) atom as, forexample, in amine groups (e.g., ═NH or —NH₂), aldehyde groups, anhydridegroups, carboxylic groups (—COOH), hydroxyl groups (—OH), thiol groups(—SH); isocyanate (—NCO) or blocked isocyanate groups; ketone groups;any of the other functional groups described herein; or variants thereof(e.g., neutralized groups). In some embodiments, the functional groupmay be carbon-carbon double bonds.

Examples of suitable unsaturated compounds may include crotonic acid,furfuryl alcohol, furaldehyde, hydroxypropyl sorbate, sorbic acid, vinylacetic acid and mixtures or derivates thereof. Additional examples ofsuitable unsaturated compounds may include: 2,4-hexadienoic acid(E)-1-trimethylsilyloxy-1,3-butadiene, (E)-2,4-pentadienoic acid,(E)-1-amino-1,3-butadiene, (E)-1-amido-1,3-butadiene,2-trimethylsilyloxy-1,3-butadiene,(E)-1-methoxy-3-trimethylsilyloxy-1,3-butadiene, vinylnaphthalene,vinyldihydronaphthalene, vinylphenanthrene, vinylindole,vinylbenzofuran, vinylbenzothiophene, cyclohexa-2,4-dienone,o-benzoquinone, and mixtures thereof.

In some embodiments, salt or salt-forming groups are preferredfunctional groups for inclusion in the unsaturated compound. Acid oranhydride groups are particularly preferred in some embodiments.

In some embodiments, the unsaturated compound includes at least oneallylic hydrogen, more preferably two allylic hydrogens attached to asame carbon atom. In an embodiment, the unsaturated compound has thestructure (H)(W¹)C—C(W²)═C(W³)(W⁴), wherein each of W¹ to W⁴ isindependently any suitable atom or group, with the proviso that at leastone of W¹ to W⁴ includes a functional group, more preferably afunctional group disclosed herein. In preferred embodiments, W¹ is ahydrogen atom and at least one of W², W³, or W⁴ includes a functionalgroup, more preferably a salt or salt-forming group.

The reaction between the unsaturated compound and the unsaturatedprecursor polymer typically consumes one or more double bonds andresults in the formation of one or more covalent attachments between theunsaturated compound and the unsaturated precursor polymer. In someembodiments, the one or more covalent attachments are each carbon-carbonsingle bonds.

In certain preferred embodiments, the unsaturated compound includes twoor more conjugated carbon-carbon double bonds. By way of example, acompound having a —C(R)═C(R)—C(R)═C(R)— segment is a conjugated diene,where each R independently denotes any suitable atom (e.g., hydrogen, ahalogen, etc.) or group. Examples of conjugated unsaturated compoundsmay include furfuryl alcohol, furaldehyde, hydroxypropyl sorbate, sorbicacid, and the like. Sorbic acid is a preferred conjugated unsaturatedcompound. By way of example, other suitable functionalized conjugatedunsaturated compounds may include functionalized variants of any of thefollowing: anthracene, butadiene (including, e.g., dimethyl butadiene),cyclohexadiene, cyclopentadiene (including, e.g., 1-alkylcyclopentadienes or 2-alkyl cyclopentadienes), furan, isoprene, methylvinyl ketone, thiophene, and mixtures thereof.

In preferred embodiments, the unsaturated compound is reacted with theunsaturated precursor polymer to form a covalently attached side groupderived from the unsaturated compound and having one or more functionalgroups. While not intending to be bound by any theory, it is believedthat the unsaturated compound is covalently attached to the unsaturatedprecursor polymer via a reaction involving one or more double or triplebonds of the polymer to incorporate one or more side groups having thedesired function group(s). In particular, it is believed that inpreferred embodiments the reaction proceeds via a Diels-Alder reactionmechanism and/or an Ene reaction mechanism. Depending upon the materialsused and the reaction conditions, it is believed that both Diels-Alderand Ene reactions can occur, which results in the incorporation of sidegroups having different structures. Diels-Alder and Ene reactions areboth members of the “pericyclic” family of chemical reactions, althoughcertain Ene reactions may be non-pericyclic reactions (e.g., certain Enereactions in which a Lewis acid catalyst is used). It is also possiblethat one or more other pericyclic reactions may occur.

Diels-Alder reactions (often referred to as [4+2] cycloadditions)typically involve the addition of an unsaturated component (oftenreferred to as a “dienophile” in the context of a Diels-Alder reaction)across the 1,4 position of a conjugated diene component to form acycloaddition reaction product that is typically cyclic or bicyclic innature. In some situations, at least one of the conjugated diene andunsaturated components contains one or more substituents that “activate”the component toward reaction, although in some instances one or bothcomponents can contain a “deactivating” substituent or substituents. TheDiels-Alder reaction is generally considered to be a concerted reaction,and as such, either component can be the “electron donor” or “electronacceptor” depending upon the substituents bonded thereto. By way ofexample, a schematic diagram of the reaction mechanism thought to occurduring a Diels-Alder reaction between sorbic acid and an unsaturatedstructural unit derived from maleic anhydride is depicted below,including the resulting functionalized side group.

Thus, in some embodiments, the side group is attached to another portionof the functionalized polymer (e.g., a backbone of the polymer oranother group attached to the backbone) via a cyclic group, which mayoptionally be a polycyclic group (e.g., a bridged bicyclic group such asa norbornene group). When a side group is attached via a Diels-Alderreaction mechanism, an unsaturated cyclic group is believed to result atthe site of covalent attachment. The resulting unsaturated cyclic groupmay optionally be hydrogenated, if desired, to yield a saturated cyclicgroup

In contrast, the reaction mechanism thought to occur if an Ene reactionoccurs between sorbic acid and an unsaturated structural unit derivedfrom maleic anhydride is depicted below, including the resultingfunctionalized side group.

Unlike a Diels-Alder reaction mechanism, an Ene reaction mechanism doesnot require an unsaturated conjugated diene component. As such, when anEne reaction mechanism is employed, a mono-unsaturated compound may beused (e.g., vinyl acetic acid) to incorporate a side group of thepresent disclosure. Ene reactions typically require that at least oneallylic hydrogen is present, more preferable two allylic hydrogensattached to a same carbon atom. As depicted in the above reactiondiagram, the covalently attached side group resulting from the Enereaction is thought to include a double bond that includes a carbon atomto which an allylic hydrogen was attached prior to reaction.

In some embodiments, a Diels-Alder or Ene reaction mechanism may be usedto covalently attach an unsaturated compound to an unsaturated pendantgroup of the unsaturated precursor polymer. In such embodiments, theresulting polymer includes at least one functional-group-containing sidegroup that is not attached directly to a backbone of the polymer.

A Diels-Alder or Ene reaction may also be used to “endcap” one or moreterminal ends of a backbone of the unsaturated precursor polymer with astructural unit derived from the unsaturated compound in order toprovide one or more functional groups.

While any suitable double or triple bonds may be included in theunsaturated precursor polymer, carbon-carbon double bonds andcarbon-carbon triple bonds are preferred, with carbon-carbon doublebonds being presently preferred. If desired, the double bonds may beconjugated double bonds, more preferably conjugated carbon-carbon doublebonds. The unsaturated precursor polymer can have any suitable backbone,including any type of backbone previously described herein. In certainpreferred embodiments, the unsaturated precursor polymer has a polyesterbackbone, which may optionally include any other suitable linkages aspreviously discussed.

As discussed above, carbon-carbon double bonds are preferred for boththe unsaturated compound and the unsaturated precursor polymer. Examplesof other suitable double bonds may include carbon-oxygen double bonds,carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, ornitrogen-oxygen double bonds. Preferred double bonds are capable ofparticipating in one or both of a Diels-Alder reaction and an Enereaction.

In another aspect, the present disclosure provides a water-dispersiblepolymer having one or more water-dispersing groups, at least one ofwhich has preferably been incorporated into the polymer using thefunctionalization method of the present disclosure. Thewater-dispersible polymer preferably has utility as a binder polymer foruse in water-based coating compositions, including, e.g., water-basedpackaging coating compositions, and is preferably included in suchcompositions in at least a film-forming amount.

In general, it is difficult to take a binder polymer having utility insolvent-based coating compositions and successfully disperse it into anaqueous medium to produce a water-based coating composition thatexhibits suitable coating properties when cured. This is especially truein the area of packaging coatings (e.g., food or beverage can coatings),where coating compositions must exhibit a stringent balance of difficultto achieve coating properties. Conventional water-dispersing techniques,when applied, for example, to polyester polymers having utility insolvent-based packaging coating compositions, often yield water-basedpackaging coatings having inferior coating properties. However, it hasbeen surprisingly discovered that the materials and methods of thepresent disclosure can be used to modify a polyester binder polymerhaving utility in solvent-based packaging coating compositions toproduce a water-dispersible variant thereof that can be formulated intoa water-based packaging coating composition that exhibits coatingproperties, when cured, that are comparable to that of the curedsolvent-based coating composition.

The water-dispersible polymer can include any suitable water-dispersinggroups. In preferred embodiments, the water-dispersible polymer includeswater-dispersing groups in the form of one or more salt groups such as,for example, anionic or cationic salt groups (e.g., neutralized acid orbase groups), or a combination thereof.

Examples of suitable salt groups include anionic groups, cationicgroups, and combinations thereof. Examples of anionic salt groupsinclude neutralized acid or anhydride groups, sulphate groups (—OSO₃ ⁻),phosphate groups (—OPO₃ ⁻), sulfonate groups (—SO₂O⁻), phosphinategroups (—POO⁻), phosphonate groups (—PO₃ ⁻), and combinations thereof.Examples of suitable cationic salt groups include:

(referred to, respectively, as quaternary ammonium groups, quaternaryphosphonium groups, and tertiary sulfate groups) and combinationsthereof. Presently preferred salt groups include neutralized acid oranhydride groups and neutralized base groups, with neutralizedcarboxylic groups being preferred in certain embodiments.

Non-limiting examples of neutralizing agents for forming anionic saltgroups include inorganic and organic bases such as an amines, sodiumhydroxide, potassium hydroxide, lithium hydroxide, ammonia, and mixturesthereof. In certain embodiments, tertiary amines are preferredneutralizing agents. Non-limiting examples of suitable tertiary aminesinclude trimethyl amine, dimethylethanol amine (also known asdimethylamino ethanol), methyldiethanol amine, triethanol amine, ethylmethyl ethanol amine, dimethyl ethyl amine, dimethyl propyl amine,dimethyl 3-hydroxy-1-propyl amine, dimethylbenzyl amine, dimethyl2-hydroxy-1-propyl amine, diethyl methyl amine, dimethyl1-hydroxy-2-propyl amine, triethyl amine, tributyl amine, N-methylmorpholine, and mixtures thereof.

Examples of suitable neutralizing agents for forming cationic saltgroups include organic and inorganic acids such as formic acid, aceticacid, hydrochloric acid, sulfuric acid, and combinations thereof.

In preferred embodiments, some or all of the salt groups of thewater-dispersible polymer are provided using the functionalizationmethod of the present disclosure and an unsaturated compound having: (i)one or more double bonds, more preferably one or more carbon-carbondouble bonds and (ii) one or more salt or salt-forming groups.

The incorporation of one or more water-dispersing groups into thepolymer via reaction with the unsaturated compound can occur at anysuitable time during the polymer synthesis. For example, a preformedunsaturated polymer of the desired molecular weight may be post-reactedwith the unsaturated compound to provide the desired number ofwater-dispersing groups.

In other embodiments, an unsaturated prepolymer may be reacted with theunsaturated compound and the resulting functionalized prepolymer can befurther upgraded to produce a functionalized polymer having the desiredfinal molecular weight. In certain such situations, however, care shouldbe exercised to avoid gelling. For example if the unsaturated compoundis an acid-functional compound such as, for example, sorbic acid, andthe prepolymer has acid and/or hydroxyl groups on each end, then theresulting prepolymer will have three or more acid and/or hydroxylgroups, which may lead to gelling problems if the prepolymer is reactedwith additional polyfunctional compounds (e.g., diacids and/or diols) tofurther upgrade the molecular weight. Such potential gelling issues areabsent when a preformed unsaturated polymer of the desired molecularweight is reacted with the unsaturated compound.

Any suitable unsaturated compound having a suitable salt or salt-forminggroup may be employed to form the water-dispersible polymer. Theunsaturated compound may include any suitable such groups describedherein. Neutralizable acid or base groups are preferred salt-forminggroups.

The unsaturated compound having one or more salt or salt-forming groupspreferably includes at least one double bond capable of participating ina Diels-Alder reaction or an Ene reaction, with carbon-carbon doublebonds being preferred. Conjugated double bonds are preferred in certainembodiments (e.g., where a Diels-Alder reaction is desired), withconjugated carbon-carbon double bonds being particularly preferred.

In embodiments in which an unsaturated compound having conjugated doublebonds is used, the unsaturated polymer may include any suitableproportion of Ene incorporated or Diels-Alder incorporated side groupsof the present disclosure. In some embodiments, both Ene and Diels-Alderreaction product side groups are present, with a substantial portion ofthe overall functional-group-containing side groups of the presentdisclosure incorporated via an Ene reaction(e.g., >10%, >25%, >50%, >60%, >70%, etc.). When both types of sidegroups are present, the Diels-Alder and Ene reaction product side groupscan be present on same polymer strands, on different polymer strands, ora combination thereof.

While the salt-group-containing or salt-forming-group-containingunsaturated compound can be of any suitable atomic weight, in presentlypreferred embodiments, it has an atomic weight of less than about 200(e.g., less than 200, less than 175, less than 150, less than 125, lessthan 100, etc.). While long-chain (e.g., >C12) and very-long chain(e.g., >C22) unsaturated fatty acids may be used, such unsaturatedcompounds are not presently preferred, especially if the polymer is tobe used in certain food-contact packaging coating applications.

Examples of suitable unsaturated compounds having salt or salt-forminggroups include sorbic acid (also referred to as 2,4-hexadienoic acid),2,4-pentadienoic acid, furoic acid, 1-amino-1,3-butadiene,1-naphthaleneacetic acid, anthracene carboxylic acid, 1,8-naphthalicanhydride, 1-naphthalene methylamine, vinyl acetic acid, neutralizedvariants thereof, and combinations thereof. Sorbic acid is a preferredunsaturated compound for use in forming the water-dispersible polymer.

The water-dispersible polymer can include any desired number of sidegroup(s) derived from the unsaturated compound having one or more saltor salt-forming groups. In some embodiments, the water-dispersiblepolymer includes at least about 0.5% by weight, more preferably at least1% by weight, and even more preferably at least about 2% by weight ofsuch side groups. Although the maximum amount of such side groups is notrestricted, the water-dispersible polymer will typically include sidegroups in an amount of less than about 50% by weight, more typicallyless than about 30% by weight, even more typically less than about 7% byweight. The above side group concentrations are based on the amount ofunsaturated compound included in the reaction mixture relative to thetotal nonvolatile weight of reactants used to make the water-dispersiblepolymer.

The discussion that follows provides representative materials andmethods for making water-dispersible polyester polymers of the presentdisclosure, as well as coating compositions formulated therefrom. Theteachings of the below discussion may be applicable to other embodimentsof the present disclosure as well.

The water-dispersible polyester polymer may include polymer segmentsother than polyester segments. Typically, however, at least 50 wt-% ofthe polyester will comprise polyester segments. In some embodiments,substantially all (e.g., >80 wt-%, >90 wt-%, >95 wt-%, etc.), or all, ofthe polyester on a weight basis comprises polyester segments.

The unsaturated polyester precursor polymer may be prepared usingstandard condensation reactions. The polyester precursor is typicallyderived from a mixture of at least one polyfunctional alcohol (“polyol”)esterified with at least one polycarboxylic acid (or derivativethereof). The reaction mixture preferably includes at least oneunsaturated reactant. In some embodiments, a transesterificationpolymerization may be used. If desired, the unsaturated polyesterprecursor polymer may include polymer linkages (e.g., amide, carbamate,carbonate ester, ether, urea, urethane, etc.), side chains, and endgroups not related to simple polyol and polyacid components.

Any suitable reaction process may be used to make the polymers of thepresent disclosure. Suitable such processes include, for example,processes in which polymerization occurs in the presence of a solventsuch as reflux polymerization processes as well as processes in whichpolymerization occurs in the absence of added solvent such as melt-blendpolymerization processes.

In some embodiments, it may be advantageous to use a polymerizationprocess in which solvent is not required. Benefits associated with suchprocesses may include the ability to process at reaction temperatures inexcess (e.g., >230° C.) of the reflux temperature of common solvents,enhanced reaction kinetics, the avoidance of solubility issues that maybe associated with the use of certain solvents, and the ability toproduce higher molecular weight polymers. In some embodiments, asubstantially solvent-free polymerization process may be employed inwhich the reactants are preferably reacted at a high temperature(e.g., >250° C.) under a reduced pressure. In such solvent-freepolymerizations processes, the reaction mixture is typically agitatedduring polymerization using a high-torque mixing unit that is preferablycapable of handling the viscosities typically associated with very highmolecular weight polymers in the absence of added solvents or diluent.The finished polymer is typically ejected from the reactor as a solid“strand”, which can be chopped into pellets of a desired size, which cansubsequently be dissolved in a suitable liquid if desired. Suchsolvent-less polymerization processes can be used, for example, toproduce polyester polymers having a Mn of greater than about 10,000,such as from about 10,000 to about 30,000.

Any suitable unsaturated reactants may be used to incorporate doubleand/or triple bonds into the unsaturated polyester precursor polymer.Such unsaturated reactants will typically include at least one reactivefunctional group capable of participating in a condensation and/orstep-growth polymerization, and more typically will include two or moresuch reactive functional groups, with two such functional groups beingpreferred in some embodiments. Examples of such reactive functionalgroups include any of the active hydrogen groups disclosed herein, aswell as any other suitable reactive functional groups such as, forexample, isocyanate (—NCO) groups. Reactive functional groups capable ofparticipating in ester-forming reactions (e.g., hydroxyl groups,carboxylic groups, anhydride groups, etc.) are examples of preferredsuch reactive functional groups. Unsaturated polyacids,(poly)anhydrides, or esterified variants thereof are examples ofpreferred unsaturated reactants, with unsaturated dicarboxylic acids andunsaturated mono-anhydrides being presently preferred. Some specificexamples of suitable unsaturated reactants may include unsaturatedcarboxylic acids such as maleic acid, 2-methyl maleic acid, fumaricacid, itaconic acid, 2-methyl itaconic acid, nadic acid, methyl-nadicacid, tetrahydrophthalic acid, methyltetrahydrophthalic acid,derivatives or anhydrides thereof (e.g., maleic anhydride, nadicanhydride, and the like), and mixtures thereof. Some specific examplesof suitable unsaturated polyols may include butane diol, butyne diol,3-hexyne-2,5-diol, 2-butynedioic acid, and mixtures thereof.

Maleic anhydride is an example of a preferred compound for incorporatingunsaturation into the unsaturated polyester precursor polymer. Maleicanhydride is particularly useful for a variety of reasons, including,for example, cost and ready availability in commercial quantities.Moreover, while not intending to be bound by any theory, it is believedthat maleic anhydride is a particularly strong dienophile havingexcellent reactivity in a Diels-Alder reaction. Maleic anhydride is alsoa preferred reactant for Ene reactions. It has been observed thatDiels-Alder reactions can be conducted at a lower temperature forunsaturated polyester polymers having units derived from maleicanhydride (e.g., from about 150 to about 200° C. as opposed to, e.g.,from 260 to 280° C. as may be required for polymers having units derivedfrom unsaturated fatty acids or oils), which may be beneficial incertain embodiments in which a lower reaction temperature is desired.

In some embodiments (e.g., where the coating composition is intended foruse as a food-contact coating composition), it is preferable that theratio of unsaturated compound to unsaturation in the polyester precursorpolymer be controlled to avoid the presence of unsuitable amounts ofresidual unreacted unsaturated compound in the coating composition. Forexample, when the unsaturation of the polyester precursor is provided bymaleic anhydride (or some other such unsaturated reactant(s)), thepolyester precursor polymer preferably includes an excess, on a molarbasis, of units derived from maleic anhydride (or other unsaturatedreactants) relative to the amount of functional-group-containingunsaturated compound (e.g., sorbic acid) included in the reactionmixture. More preferably, the molar ratio of functional-group-containingunsaturated compound to unsaturated monomeric units present in thepolyester precursor is less than 0.8:1, and even more preferably lessthan 0.6:1. In some embodiments, the molar ratio offunctional-group-containing unsaturated compound to unsaturatedmonomeric units present in the polyester precursor is greater than about0.1:1, more preferably greater than about 0.2:1, and even morepreferably greater than 0.3:1. In some embodiments, the molar ratio offunctional-group-containing unsaturated compound to carbon-carbon doublebond containing monomeric units present in the polyester precursor is asdescribed above.

Examples of suitable polycarboxylic acids for preparing thewater-dispersible polyester polymer include dicarboxylic acids andpolycarboxylic acids having higher acid functionality (e.g.,tricarboxylic acids, tetracarboxylic acids, etc.) or anhydrides thereof,precursors or derivatives thereof (e.g., an esterifiable derivative of apolycarboxylic acid, such as a dimethyl ester or anhydride), or mixturesthereof. Suitable polycarboxylic acids may include, for example, maleicacid, fumaric acid, succinic acid, adipic acid, phthalic acid,tetrahydrophthalic acid, methyltetrahydrophthalic acid,hexahydrophthalic acid, methylhexahydrophthalic acid,endomethylenetetrahydrophthalic acid, azelaic acid, sebacic acid,isophthalic acid, trimellitic acid, terephthalic acid, naphthalenedicarboxylic acid, cyclohexane dicarboxylic acid, glutaric acid, dimerfatty acids, anhydrides or derivatives thereof, and mixtures thereof. Ifdesired, adducts of polyacid compounds (e.g., triacids, tetraacids,etc.) and monofunctional compounds may be used. It should be understoodthat in synthesizing the polyester, the specified acids may be in theform of anhydrides, esters (e.g., alkyl ester) or like equivalent form.For sake of brevity, such compounds are referred to herein as“carboxylic acids” or “polycarboxylic acids.”

Examples of suitable polyols include diols, polyols having three or morehydroxyl groups (e.g., triols, tetraols, etc.), and combinationsthereof. Suitable polyols may include, for example, ethylene glycol,propylene glycol, 1,3-propanediol, glycerol, diethylene glycol,dipropylene glycol, triethylene glycol, trimethylolpropane,trimethylolethane, tripropylene glycol, neopentyl glycol,pentaerythritol, 1,4-butanediol, hexylene glycol, cyclohexanedimethanol,a polyethylene or polypropylene glycol, isopropylidenebis(p-phenylene-oxypropanol-2), and mixtures thereof. If desired,adducts of polyol compounds (e.g., triols, tetraols, etc.) andmonofunctional compounds may be used.

The reaction mixture used to form the water-dispersible polyesterpolymer may include any suitable optional comonomers.

If trifunctional or higher polyols or polycarboxylic acids are includedin the reaction mixture used to make the unsaturated polyester precursorpolymer, the total amount of such reactants are preferablystoichiometrically controlled to avoid gelling. In certain preferredembodiments, trifunctional or higher polyols and polycarboxylic acidsare not included in the reaction mixture used to make the unsaturatedpolyester precursor polymer. If used, trifunctional monomer ispreferably used in an amount of less than 5% by weight, based on thetotal nonvolatile weight of the reactants used to make the unsaturatedpolyester precursor polymer.

In some embodiments, it is preferable that the water-dispersiblepolyester polymer includes one or more aromatic groups, more preferablyone or more backbone aromatic groups. Preferred aromatic polymersinclude at least about 5 wt-%, more preferably at least about 10 wt-%,even more preferably at least about 15 wt-%, and even more preferably atleast about 20 wt-% of aromatic groups. In some embodiments, the polymermay include up to 75 wt-% or more of aromatic groups. The aforementionedweight percentages correspond to the total weight of aromatic monomersused to form the polymer relative to the total weight of the reactantsused to form polymer. Thus, for example, if an oligomer having anaromatic group is incorporated into the polymer, the wt-% of thearomatic group in the polymer is calculated using the weight of thearomatic monomer used to form the oligomer (as opposed to the weight ofthe oligomer). Suitable aromatic monomers include, for example, acid-,ester-, or anhydride-functional aromatic monomers (e.g., aromaticmonoacids and/or polyacids, more preferably aromatic polyacids);hydroxyl-functional aromatic monomers (e.g., aromatic mono- and/orpolyfunctional monomers); or aromatic monomers having one or more(typically at least two) reactive groups capable of participating in acondensation and/or step-growth reaction with a complimentary reactivegroup (more preferably, a hydroxyl, carboxylic acid, ester, or anhydridegroups) to form a covalent linkage. Examples of suitable aromaticmonomers include terephthalic acid, isophthalic acid, phthalic acid,phthalic anhydride, trimellitic anhydride, trimellitic acid, dimethylterephthalate, dimethyl isophthalate, dimethyl phthalate, 5-sodiosulphoisophthalic acid, naphthalic acid, 1,8-naphthalic anhydride, dimethylnaphthalate, pyromellitic dianhydride, and derivatives and combinationsthereof.

The water-dispersible polyester polymer may have any suitable endgroups. In some embodiments, the backbone of the water-dispersiblepolyester polymer is hydroxyl-terminated and/or carboxyl-terminated,more preferably hydroxyl-terminated.

When acid or anhydride groups are used to impart water-dispersibility tothe polyester polymer, the acid- or anhydride-functional polymerpreferably has an acid number of at least 5, and more preferably atleast 40 milligrams (mg) KOH per gram resin. The acid- oranhydride-functional polyester polymer preferably has an acid number ofno greater than 400, and more preferably no greater than 100 mg KOH pergram resin.

In certain preferred embodiments, the water-dispersible polyesterpolymer is capable of being mixed with water to form a stable aqueousdispersion that does not separate into layers after being stored undernormal conditions (e.g., storage in ambient temperature withoutagitation) for 1 week, preferably 1 month, and more preferably 3 months.

The water-dispersible polyester polymer may have any suitable glasstransition temperature (“Tg”). In some embodiments, the polymer has a Tgof at least about 0° C., more preferably at least about 10° C., and evenmore preferably at least about 25° C. Although the maximum Tg is notparticularly restricted, preferably the Tg is less than about 150° C.,more preferably less than about 100° C., and even more preferably lessthan about 50° C.

The water-dispersible polyester polymer may be of any suitable molecularweight. In preferred embodiments, the water-dispersible polyesterpolymer has a number average molecular weight (Mn) of at least about2,000, more preferably at least about 4,000, and even more preferably atleast 5,000. While the upper molecular weight range is not restricted,the water-dispersible polyester polymer will typically have a Mn of lessthan about 50,000 and more typically less than 30,000. The molecularweight may vary depending on a variety of factors, including, forexample, the desired coating end use, cost, and the manufacturing methodemployed to synthesize the polymer. In embodiments in which a processingsolvent is present during polymer manufacture, the polymer willtypically have a Mn of less than about 20,000, even more typically lessthan about 10,000. In embodiments in which a melt-polymerizationmanufacturing process is used, the polymer may have a Mn of greater thanabout 10,000 or from about 10,000 to about 30,000.

In some embodiments, the water-dispersible polyester polymer ispreferably free or appreciably free of fatty acids (e.g., long-chain orvery long-chain fatty acids), oils, and/or other long-chainhydrocarbons. It is believed that the use of unsuitable amounts of suchmaterials may impart undesirable off-tastes or odors to packaged food orbeverage products that are kept in prolonged contact with the coatingcompositions of the present disclosure. When used in interior beer cancoatings, the presence of unsuitable amounts of such materials in thepolymer may diminish the “head” on the beer product. In addition, thepresence of unsuitable amounts of such materials in the polymer maycause the corrosion resistance of coating compositions of the presentdisclosure to be unsuitable for certain end uses, especially forpackaging coatings intended for use with so called “hard-to-hold” foodor beverage products. In certain preferred embodiments, thewater-dispersible polyester polymer includes no more than 10 wt-%, morepreferably no more than 3 wt-%, and even more preferably no more than 1wt-% of fatty acids, oils, or other “long-chain” hydrocarbons (e.g.,having 8 or more carbon atoms such as >C10, >C12, >C15, >C20, >C30),based on the total non-volatile weight of the reactants used to make thewater-dispersible polyester polymer.

It is contemplated that, in certain embodiments, the water-dispersiblepolyester polymer may include some long-chain hydrocarbons having 12 orless carbon atoms such as, for example, sebacic acid.

In certain preferred embodiments, the water-dispersible polyesterpolymer is not an alkyd resin.

Similarly, presently preferred coating compositions of the presentdisclosure are preferably free, or appreciably free, of fatty acids(e.g., long-chain or very long-chain fatty acids) and oils. Preferredcoating compositions include no more than 20 wt-%, more preferably nomore than 10 wt-%, and even more preferably no more than 5 wt-% of oilsand fatty acids, based on the total nonvolatile weight of the coatingcomposition.

In some embodiments, the water-dispersible polyester polymer has abackbone that includes one or more “soft” segments and one or more“hard” segments, and preferably at least two hard segments. In some suchembodiments, the polyester polymer includes a plurality of hard segmentsand preferably has a Tg of from about 10° C. to about 50° C., morepreferably from about 15° C. to about 35° C. The one or more hardsegments preferably have a Tg from about 10° C. to about 100° C., morepreferably from about 15° C. to about 80° C., even more preferably fromabout 20° C. to about 70° C. In one embodiment, the hard segment has aTg of from 20° C. to 40° C. Typically, the one or more hard segments areformed from an oligomer or polymer having an Mn of at least 500, morepreferably at least 750, and even more preferably at least 1,000.

The material or materials used to generate the one or more soft segmentsare preferably selected such that the one or more soft segmentscontribute to (i) a lower overall Tg for the polyester polymer (e.g., ascompared to a polyester polymer of a similar molecular weight lackingthe one or more soft segments) and/or (ii) enhanced fabricationproperties (e.g., flexibility) for a coating composition formulatedusing the polyester polymer. Examples of materials for use in formingthe soft segment (either neat or in combination with one or morecomonomers) include adipic acid; azelaic acid; fatty acid-basedmaterials such as fatty acid dimers or dimer fatty diols; sebacic acid;succinic acid; glutaric acid; a derivative or variant thereof; or amixture thereof. In some embodiments, a soft segment is derived from oneof the above monomers without the use of any additional comonomers. Whenthe soft segment is a polyester oligomer or polymer, the aforementionedmonomers may be used in combination with one or more suitable comonomersto generate the soft segment.

Representative materials and methods for producing a polyester polymerhaving hard and soft segments are described in International PublicationNo. WO/2012/051540. For purposes of the present disclosure, in order toproduce water-dispersible variants of the solvent-based polyesterpolymers described in WO/2012/051540 using the method of the presentdisclosure, the reactants used to produce the polymer preferablyincludes one or more unsaturated reactants described herein (e.g.,maleic anhydride) to allow for functionalization of the polymer withwater-dispersing groups using the method of the present disclosure. Ithas been discovered that such water-dispersible polyester polymersexhibit superior properties when used as a binder polymer for certainwater-based, food-contact packaging coating compositions, including,e.g., beverage can end coating compositions.

The hard and soft segments may be organized in any suitableconfiguration. In some embodiments, the backbone of thewater-dispersible polyester polymer includes an alternating sequence ofhard and soft segments. In such embodiments, the alternating hard andsoft segments are typically connected to one another via step-growthlinkages, more typically condensation linkages such as ester linkages. Arepresentative example of such an alternating polymer is provided belowin Formula I:

(R²)_(r)-([HARD]-X_(S)-[SOFT]-X_(S))_(n)—(R³)_(r)

where:

-   -   [HARD] independently denotes a hard segment;    -   [SOFT] independently denotes a soft segment;    -   each X, if present, is independently a divalent organic group,        and more preferably a step-growth linkage such as, e.g., a        condensation linkage;    -   each s is independently 0 or 1, more preferably 1;    -   n is 1 or more, more preferably 1 to 15;    -   R², if present, is a reactive functional group (e.g., —OH,        —COOH, etc.), an organic group, or a soft segment that may        optionally include a terminal reactive functional group and may        optionally be connected to the adjacent hard segment via a        step-growth linkage;    -   R³, if present, is a reactive functional group (e.g., —OH,        —COOH, etc.), an organic group, or a hard segment that may        optionally include a terminal reactive functional group; and    -   each r is independently 0 or 1.

In one embodiment, n is at least 2; each s is 1; each X is an esterlinkage; each r is 1; R² is a reactive functional group, more preferablya hydroxyl group; and R³ is a hard segment terminated with a reactivefunctional group, more preferably R³ is a hydroxyl-terminated hardsegment.

In some embodiments, the water-dispersible polyester polymer isterminated on each end with a hard segment, more preferably a hardsegment having a terminal reactive functional group, and even morepreferably a hydroxyl-terminated hard segment.

In some embodiments, the ratio, on a weight basis, of hard to softsegments in the water-dispersible polyester polymer is on average from1:1 to 50:1, more preferably from 8:1 to 20:1, and even more preferablyfrom 10:1 to 15:1 (hard segments:soft segments).

The water-dispersible polyester polymer may include any number of hardand soft segments. In preferred embodiments, the polyester polymerincludes, on average, from 1 to 35, more preferably from 2 to 20, andeven more preferably from 4 to 10 of each of the hard and soft segments.In preferred embodiments, the polyester polymer includes, on average, wsoft segments (where “w” is the average number of soft segments) and w+1hard segments (e.g., when w is 3, w+1 is 4).

In some embodiments, the hard and soft segments constitute at least asubstantial majority of the polyester polymer on a weight basis. In somesuch embodiments, the hard and soft segments constitute at least 70wt-%, at least 85 wt-%, or at least 90 wt-% of the polyester polymer ofthe present disclosure. The above weight percentages include any linkagegroups (e.g., ester linkages) linking the hard and soft segments thatare formed via reaction of complimentary reactive functionalities (e.g.,hydroxyl and carboxylic groups) present on precursor hard and softsegment reactants.

The water-dispersible polyester polymer may have utility in a variety ofdifferent coating end uses. It has been discovered that thewater-dispersible polyester polymer is particularly useful in packagingcoating applications, including food or beverage container applications.The discussion that follows pertains to coating compositions formulatedusing the water-dispersible polyester polymer and having utility inpackaging coating end uses. While the discussion that follows focuses onpackaging coating compositions, it is within the scope of the presentdisclosure to apply the teachings to coating compositions intended forother end uses.

Coating compositions of the present disclosure may include any suitableamount of the water-dispersible polyester polymer to produce the desiredresult. Preferred coating compositions include at least about 50 wt-%,more preferably at least about 60 wt-%, and even more preferably atleast about 70 wt-% of the water-dispersible polyester polymer.Preferred coating compositions include up to about 100 wt-%, morepreferably up to about 95 wt-%, and even more preferably up to about 80wt-% of the water-dispersible polymer. These weight percentages arebased on the total weight of resin solids present in the coatingcomposition. While the total amount of resins solids in the coatingcomposition may vary greatly depending on the particular embodiment andmay be any suitable amount, resin solids will typically constitute atleast a majority of the total nonvolatile weight of the coatingcomposition.

The coating composition preferably further comprises a crosslinkingresin. For example, any of the well known hydroxyl-reactive curingresins can be used. The choice of particular crosslinker typicallydepends on the particular product being formulated. Examples of suitablecrosslinkers include aminoplasts, phenoplasts, blocked isocyanates, andcombinations thereof.

Phenoplast resins include the condensation products of aldehydes withphenols. Formaldehyde and acetaldehyde are preferred aldehydes. Variousphenols can be employed such as, for example, phenol, cresol,p-phenylphenol, p-tert-butylphenol, p-tert-amylphenol, andcyclopentylphenol.

Aminoplast resins include, for example, the condensation products ofaldehydes such as formaldehyde, acetaldehyde, crotonaldehyde, andbenzaldehyde with amino- or amido-group-containing substances such asurea, melamine, and benzoguanamine. Examples of suitable aminoplastresins include benzoguanamine-formaldehyde resins, melamine-formaldehyderesins, esterified melamine-formaldehyde, urea-formaldehyde resins, andcombinations thereof.

Condensation products of other amines and amides can also be employedsuch as, for example, aldehyde condensates of triazines, diazines,triazoles, guanadines, guanamines and alkyl- and aryl-substitutedmelamines. Some examples of such compounds are N,N′-dimethyl urea,benzourea, dicyandimide, formaguanamine, acetoguanamine, glycoluril,ammelin 2-chloro-4,6-diamino-1,3,5-triazine,6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole,triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine, 3,4,6-tris(ethylamino)-1,3,5-triazine, and the like. While the aldehyde employed istypically formaldehyde, other similar condensation products can be madefrom other aldehydes, such as acetaldehyde, crotonaldehyde, acrolein,benzaldehyde, furfural, glyoxal and the like, and mixtures thereof.

Examples of suitable isocyanate crosslinkers include blocked ornon-blocked aliphatic, cycloaliphatic or aromatic di-, tri-, orpoly-valent isocyanates, such as hexamethylene diisocyanate (HMDI),cyclohexyl-1,4-diisocyanate and the like, and mixtures thereof. Examplesof generally suitable isocyanates for use in such crosslinkers includeisomers of isophorone diisocyanate, dicyclohexylmethane diisocyanate,toluene diisocyanate, diphenylmethane diisocyanate, phenylenediisocyanate, tetramethyl xylene diisocyanate, xylylene diisocyanate,and mixtures thereof.

The level of curing agent used will depend, for example, on the type ofcuring agent, the time and temperature of the bake, and the molecularweight of the polymer. When used, the crosslinker is typically presentin an amount ranging from about 5 to about 40% by weight. Preferably,the crosslinker is present in an amount ranging from between 10 to 30%by weight; and more preferably, from 15 to 25% by weight. These weightpercentages are based upon the total weight of the resin solids in thecoating composition.

If desired, the coating composition may optionally include one or morevinyl polymers. An example of a preferred vinyl polymer is an acryliccopolymer, with acrylic copolymers having pendant glycidyl groups beingpreferred in some embodiments. Suitable such acrylic copolymers aredescribed in U.S. Pat. No. 6,235,102. When present, the optional acryliccopolymer is typically present in an amount from 1 to 20% by weight.Preferably, the acrylic copolymer is present in an amount from 2 to 15%by weight; more preferably, from 3 to 10% by weight; and optimally, from5 to 10% by weight. These weight percentages are based upon the totalweight of the resin solids in the coating composition.

Suitable acrylic copolymers having pendant glycidyl groups preferablycontain about 30 to 80 wt-%, more preferably about 40 to 70 wt-%, andmost preferably about 50 to 70 wt-%, of a monomer containing a glycidylgroup. Suitable monomers containing a glycidyl group include any monomerhaving a carbon-carbon double bond and a glycidyl group. Typically, themonomer is a glycidyl ester of an alpha, beta-unsaturated acid, oranhydride thereof. Suitable alpha, beta-unsaturated acids includemonocarboxylic acids or dicarboxylic acids. Examples of such carboxylicacids include acrylic acid, methacrylic acid, alpha-chloroacrylic acid,alpha-cyanoacrylic acid, beta-methylacrylic acid (crotonic acid),alpha-phenylacrylic acid, beta-acryloxypropionic acid, sorbic acid,alpha-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamicacid, beta-stearylacrylic acid, itaconic acid, citraconic acid,mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaricacid, tricarboxyethylene, maleic anhydride, and mixtures thereof.Specific examples of monomers containing a glycidyl group are glycidyl(meth)acrylate (i.e., glycidyl methacrylate and glycidyl acrylate),mono- and di-glycidyl itaconate, mono- and di-glycidyl maleate, andmono- and di-glycidyl formate. It also is envisioned that allyl glycidylether and vinyl glycidyl ether can be used as the monomer.

It also should be pointed out that the acrylic copolymer can initiallybe a copolymer of an alpha, beta-unsaturated acid and an alkyl(meth)acrylate, which then is reacted with a glycidyl halide ortosylate, e.g., glycidyl chloride, to position pendant glycidyl groupson the acrylate copolymer. The alpha, beta-unsaturated carboxylic acidcan be an acid listed above, for example.

In an alternative embodiment, an acrylic copolymer having pendanthydroxyl groups first is formed. The acrylic copolymer having pendanthydroxyl groups can be prepared by incorporating a monomer like2-hydroxyethyl methacrylate or 3-hydroxypropyl methacrylate into theacrylate copolymer. The copolymer then is reacted to position pendantglycidyl groups on the acrylic copolymer.

A preferred monomer containing a glycidyl group is glycidyl(meth)acrylate.

The acrylic copolymer may optionally be formed from reactants includingan alkyl (meth)acrylate having the structure: CH₂═C(R)—CO—OR⁶ wherein R⁵is hydrogen or methyl, and R⁶ is an alkyl group containing 1 to 16carbon atoms. The R⁶ group can be substituted with one or more, andtypically one to three, moieties such as hydroxy, halo, amino, phenyl,and alkoxy, for example. Suitable alkyl (meth)acrylates for use in thecopolymer therefore encompass hydroxy alkyl (meth)acrylates andaminoalkyl (meth)acrylates. The alkyl (meth)acrylate typically is anester of acrylic or methacrylic acid. Preferably, R⁵ is methyl and R⁶ isan alkyl group having 2 to 8 carbon atoms. Most preferably, R⁵ is methyland R⁶ is an alkyl group having 2 to 4 carbon atoms. Examples of thealkyl (meth)acrylate include methyl, ethyl, propyl, isopropyl, butyl,isobutyl, pentyl, isoamyl, hexyl, 2-aminoethyl, 2-hydroxyethyl,2-ethylhexyl, cyclohexyl, decyl, isodecyl, benzyl, 2-hydroxypropyl,lauryl, isobornyl, octyl, nonyl (meth)acrylates, and combinationsthereof.

The acrylic copolymer preferably includes one or more vinyl comonomerssuch as styrene, halostyrene, isoprene, diallylphthalate,divinylbenzene, conjugated butadiene, alpha-methylstyrene, vinyltoluene, vinyl naphthalene, and mixtures thereof. Other suitablepolymerizable vinyl monomers include acrylonitrile, acrylamide,methacrylamide, methacrylonitrile, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl stearate, isobutoxymethyl acrylamide, and thelike. In one embodiment, the acrylic copolymer is not made usingstyrene.

The aforementioned monomers may be polymerized by standard free radicalpolymerization techniques, e.g., using initiators such as peroxides orperoxy esters, to provide an acrylic copolymer preferably having an Mnof about 2,000 to 15,000, more preferably about 2,500 to 10,000, andmost preferably about 3,000 to 8,000. The acrylic copolymer may beproduced in situ in the presence of the polyester polymer and/or may beat least partially grafted to the polyester (e.g., via unsaturationpresent in the polyester such as may be introduced using maleicanhydride or the like).

The coating composition of the present disclosure may also include otheroptional ingredients that do not adversely affect the coatingcomposition or a cured coating composition resulting therefrom. Suchoptional ingredients are typically included in a coating composition toenhance composition esthetics, to facilitate manufacturing, processing,handling, and application of the composition, and to further improve aparticular functional property of a coating composition or a curedcoating composition resulting therefrom.

Such optional ingredients include, for example, catalysts, dyes,pigments, toners, extenders, fillers, lubricants, anticorrosion agents,flow control agents, thixotropic agents, dispersing agents,antioxidants, adhesion promoters, light stabilizers, organic solvents,and mixtures thereof. Each optional ingredient is included in asufficient amount to serve its intended purpose, but not in such anamount to adversely affect a coating composition or a cured coatingcomposition resulting therefrom.

One optional ingredient is a catalyst to increase the rate of cureand/or the extent of crosslinking. Non-limiting examples of catalysts,include, but are not limited to, strong acids (e.g., dodecylbenzenesulphonic acid (DDBSA, available as CYCAT 600 from Cytec), methanesulfonic acid (MSA), p-toluene sulfonic acid (pTSA), dinonylnaphthalenedisulfonic acid (DNNDSA), and triflic acid), quaternary ammoniumcompounds, phosphorous compounds, tin and zinc compounds, andcombinations thereof. Examples include a tetraalkyl ammonium halide, atetraalkyl or tetraaryl phosphonium iodide or acetate, tin octoate, zincoctoate, triphenylphosphine, and similar catalysts known to personsskilled in the art. If used, a catalyst is preferably present in anamount of at least 0.01 wt-%, and more preferably at least 0.1 wt-%,based on the weight of nonvolatile material in the coating composition.If used, a catalyst is preferably present in an amount of no greaterthan 3 wt-%, and more preferably no greater than 1 wt-%, based on theweight of nonvolatile material in the coating composition.

Another useful optional ingredient is a lubricant, like a wax, whichfacilitates manufacture of coated articles (e.g., food or beverage canends) by imparting lubricity to planar coated metal substrate. Alubricant is preferably present in the coating composition in an amountof about 0.1% to about 5%, and preferably about 0.3% to about 3.5%, byweight of nonvolatile material. Preferred lubricants include, forexample, Carnauba wax, polyethylene-type lubricants,polytetrofluoroethylene (PTFE)-modified polyethylene lubricants, andFisher-Tropsch lubricants.

Another useful optional ingredient is a pigment, like titanium dioxide.A pigment is optionally present in the coating composition in an amountof 0 to about 50%, by weight of nonvolatile material.

In certain preferred embodiments, the coating composition is awater-based coating composition that preferably includes at least afilm-forming amount of the water-dispersible polyester polymer of thepresent disclosure. The coating composition preferably includes at least30 wt-% of liquid carrier and more typically at least 50 wt-% of liquidcarrier. In such embodiments, the coating composition will typicallyinclude less than 90 wt-% of liquid carrier, more typically less 80 wt-%of liquid carrier. The liquid carrier is preferably at least about 50wt-% water, more preferably at least about 60 wt-% water, and even morepreferably at least of about 75 wt-% water. In some embodiments, theliquid carrier is free or substantially free of organic solvent.

In certain preferred embodiments, the water-based coating composition isstorage stable (e.g., does not separate into layers) under normalstorage conditions for at least 1 week, more preferably at least 1month, and even more preferably at least 3 months.

Other embodiments of the coating composition of the present disclosuremay be solvent-based coating compositions that include, for example, nomore than a de minimus amount (e.g., 0 to 2 wt-%) of water.

In some embodiments, the cured coating composition of the presentdisclosure preferably has a Tg of at least 20° C., more preferably atleast 25° C., and even more preferably at least 30° C. In someembodiments, the Tg of the cured coating composition is preferably lessthan about 80° C., more preferably less than about 70° C., and even morepreferably less than about 60° C.

In some embodiments, the coating composition of the present disclosure(e.g., packaging coating embodiments) prior to cure (e.g., the liquidcoating composition), includes less than 1,000 parts-per-million(“ppm”), preferably less than 200 ppm, and more preferably less than 100ppm of low-molecular weight (e.g., <500 g/mol, <200 g/mol, <100 g/mol,etc.) ethylenically unsaturated compounds.

Preferred coating compositions are substantially free of mobilebisphenol A (“BPA”) and the diglycidyl ether of BPA (“BADGE”), and morepreferably essentially free of these compounds, and most preferablycompletely free of these compounds. The coating composition is alsopreferably substantially free of bound BPA and BADGE, more preferablyessentially free of these compounds, and optimally completely free ofthese compounds. In addition, preferred compositions are alsosubstantially free, more preferably essentially free, and mostpreferably completely free of: bisphenol S, bisphenol F, and thediglycidyl ether of bisphenol F or bisphenol S.

In some embodiments, the polymer of the present disclosure (andpreferably the coating composition) is at least substantially“epoxy-free,” more preferably “epoxy-free.” The term “epoxy-free,” whenused herein in the context of a polymer, refers to a polymer that doesnot include any “epoxy backbone segments” (i.e., segments formed fromreaction of an epoxy group and a group reactive with an epoxy group).Thus, for example, a polymer having backbone segments that are thereaction product of a bisphenol (e.g., bisphenol A, bisphenol F,bisphenol S, 4,4′dihydroxy bisphenol, etc.) and a halohdyrin (e.g.,epichlorohydrin) would not be considered epoxy-free. However, a vinylpolymer formed from vinyl monomers and/or oligomers that include anepoxy moiety (e.g., glycidyl methacrylate) would be consideredepoxy-free because the vinyl polymer would be free of epoxy backbonesegments.

In some embodiments, the coating composition is “PVC-free.” That is, thecoating composition preferably contains less than 2 wt-%, morepreferably less than 0.5 wt-%, and even more preferably less than 1 ppmof vinyl chloride materials or other halogen-containing vinyl materials.

Coating compositions of the present disclosure may be prepared byconventional methods in various ways. For example, the coatingcompositions may be prepared by simply admixing the functionalizedpolymer, optional crosslinker and any other optional ingredients, in anydesired order, with sufficient agitation. The resulting mixture may beadmixed until all the composition ingredients are substantiallyhomogeneously blended. Alternatively, the coating compositions may beprepared as a liquid solution or dispersion by admixing an optionalcarrier liquid, functionalized polymer, optional crosslinker, and anyother optional ingredients, in any desired order, with sufficientagitation. An additional amount of carrier liquid may be added to thecoating compositions to adjust the amount of nonvolatile material in thecoating composition to a desired level.

In some embodiments, the functionalized polymer is polymerized inorganic solvent and base or acid groups present on the functionalizedpolymer are at least partially neutralized to disperse the polymer intoaqueous medium to form a stable aqueous dispersion for furtherformulation.

Cured coatings of the present disclosure preferably adhere well to metal(e.g., steel, tin-free steel (TFS), tin plate, electrolytic tin plate(ETP), aluminum, etc.) and provide high levels of resistance tocorrosion or degradation that may be caused by prolonged exposure toproducts such as food or beverage products. The coatings may be appliedto any suitable surface, including inside surfaces of containers,outside surfaces of containers, container ends, and combinationsthereof.

The coating composition of the present disclosure can be applied to asubstrate using any suitable procedure such as spray coating, rollcoating, coil coating, curtain coating, immersion coating, meniscuscoating, kiss coating, blade coating, knife coating, dip coating, slotcoating, slide coating, and the like, as well as other types ofpremetered coating. In an embodiment where the coating is used to coatmetal sheets or coils, the coating can be applied by roll coating.

The coating composition can be applied on a substrate prior to, orafter, forming the substrate into an article. In some embodiments, atleast a portion of a planar substrate is coated with one or more layersof the coating composition of the present disclosure, which is thencured before the substrate is formed into an article (e.g., viastamping, drawing, draw-redraw, etc.).

After applying the coating composition onto a substrate, the compositioncan be cured using a variety of processes, including, for example, ovenbaking by either conventional or convectional methods. The curingprocess may be performed in either discrete or combined steps. Forexample, the coated substrate can be dried at ambient temperature toleave the coating composition in a largely un-crosslinked state. Thecoated substrate can then be heated to fully cure the coatingcomposition. In certain instances, the coating composition can be driedand cured in one step. In preferred embodiments, the coating compositionof the present disclosure is a heat-curable thermoset coatingcomposition.

The coating composition of the present disclosure may be applied, forexample, as a mono-coat direct to metal (or direct to pretreated metal),as a primer coat, as an intermediate coat, as a topcoat, or anycombination thereof.

Preferred coating compositions of the present disclosure formulatedusing the water-dispersible polyester polymer are particularly useful asadherent coatings on interior or exterior surfaces of metal packagingcontainers. Non-limiting examples of such articles include closures(including, e.g., internal surfaces of twist-off caps for food andbeverage containers); internal crowns; two and three-piece metal cans(including, e.g., food and beverage cans); shallow drawn cans; deepdrawn cans (including, e.g., multi-stage draw and redraw food cans); canends (including, e.g., riveted beverage can ends and easy open canends); monobloc aerosol containers; and general industrial containers,cans, and can ends; and drug cans such as metered-dose-inhaled (“MDI”)cans.

The aforementioned coating compositions formulated using thewater-dispersible polyester polymerare particularly well adapted for useas a coating for two-piece cans, including two-piece cans having ariveted can end for attached a pull tab thereto. Two-piece cans aremanufactured by joining a can body (typically a drawn metal body) with acan end (typically a drawn metal end). In preferred embodiments, thecoating compositions are suitable for use in food-contact situations andmay be used on the inside of such cans. The coatings are also suited foruse on the exterior of the cans. Notably, the coatings are well adaptedfor use in a coil coating operation. In this operation, a coil of asuitable substrate (e.g., aluminum or steel sheet metal) is first coatedwith the coating composition (on one or both sides), cured (e.g., usinga bake process), and then the cured substrate is formed (e.g., bystamping or drawing) into the can end or can body or both. The can endand can body are then sealed together with a food or beverage containedtherein.

Such coating compositions are particularly well adapted for use as aninternal or external coating on a riveted beverage can end (e.g., a beeror soda can end). Preferred embodiments exhibit an excellent balance ofcorrosion resistance and fabrication properties (including on the harshcontours of the interior surface of the rivet to which the pull tabattaches) when applied to metal coil that is subsequently fabricatedinto a riveted beverage can end.

Below are some test methods useful for assessing the coating propertiesof certain embodiments of the coating composition of the presentdisclosure. The results of the below tests A-G for certain coatingsprepared according to the present disclosure are presented in Table 1below.

A. Adhesion Test

Adhesion testing is performed to assess whether the coating adheres tothe coated substrate. The adhesion test was performed according to ASTMD 3359—Test Method B, using SCOTCH 610 tape, available from 3M Companyof Saint Paul, Minn. Adhesion is generally rated on a scale of 0-10where a rating of “10” indicates no adhesion failure, a rating of “9”indicates 90% of the coating remains adhered, a rating of “8” indicates80% of the coating remains adhered, and so on. Adhesion ratings of 10are typically desired for commercially viable coatings. B. BlushResistance Test

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount of waterabsorbed into a coated film. When the film absorbs water, it generallybecomes cloudy or looks white. Blush is generally measured visuallyusing a scale of 0-10 where a rating of “10” indicates no blush and arating of “0” indicates complete whitening of the film. Blush ratings ofat least 7 are typically desired for commercially viable coatings andoptimally 9 or above. C. Water Pasteurization Test

This is a measure of the coating integrity of the coated substrate afterexposure to heat while in contact with water. This test provides anindication of an ability of a coating to withstand conditions frequentlyassociated with food or beverage preservation or sterilization. For thepresent evaluation, coated substrate samples (in the form of flatpanels) were placed in a vessel and partially immersed in DI water.Testing is accomplished by subjecting the immersed coated substrate toheat of 66 C° at atmospheric pressure for a period of 90 minutes. Thecoated substrate was then tested for adhesion and blush as describedabove. In food or beverage applications requiring water pasteurizationperformance, adhesion ratings of 10 and blush ratings of at least 7 aretypically desired for commercially viable coatings.

D. Water Retort Test

Retort performance is not necessarily required for all food and beveragecoatings, but is desirable for some product types that are packed underretort conditions. For the present evaluation, coated substrate samples(in the form of flat panels) were placed in a vessel and partiallyimmersed in DI water. While partially immersed in the test substance,the coated substrate samples were placed in a pressure cooker andsubjected to heat of 121° C. above atmospheric pressure (using apressure suitable to achieve the desired temperature) for a time periodof 90 minutes. After retort, the coated substrate samples were allowedto sit for at least 2 hours before being tested for adhesion, blushresistance, or stain resistance. In food or beverage applicationsrequiring retort performance, after retort, adhesion ratings of 10 andblush ratings of at least 7 are typically desired for commerciallyviable coatings.

E. Fabrication Test

This test provides an indication of the level of flexibility of acoating. Moreover, this test measures the ability of a coating to retainits integrity as it undergoes the formation process necessary to producea food or beverage can end. In particular, it is a measure of thepresence or absence of cracks or fractures in the formed end. To besuitable for food or beverage can end applications, a coatingcomposition should preferably exhibit sufficient flexibility toaccommodate the extreme contour of the rivet portion of the easy openfood or beverage can end.

The end is typically placed on a cup filled with an electrolytesolution. The cup is inverted to expose the surface of the end to theelectrolyte solution. The amount of electrical current that passesthrough the end is then measured. If the coating remains intact (nocracks or fractures) after fabrication, minimal current will passthrough the end.

For the present evaluation, fully converted 202 standard opening rivetedbeverage can ends were exposed for a period of 4 seconds to anelectrolyte solution comprised of 1% NaCl by weight in deionized water.Metal exposures were measured using a WACO Enamel Rater II, availablefrom the Wilkens-Anderson Company, Chicago, Ill., with an output voltageof 6.3 volts. The measured electrical current, in milliamps, isreported. End continuities are typically tested initially and then afterthe ends are subjected to pasteurization or retort.

A coating is considered herein to satisfy the Fabrication Test if itpasses an electric current (after end formation) of less than about 10milliamps (mA) when tested as described above. Preferred coatingcompositions for use on riveted beverage cans ends exhibit an electriccurrent of less than 5 mA, more preferably less than 1 mA. The resultsof this test for certain coatings prepared according to the presentdisclosure are presented in Table 1—both before and after Dowfaxtesting.

F. Dowfax Detergent Test

The “Dowfax” test is designed to measure the resistance of a coating toa boiling detergent solution. The solution is prepared by mixing 5 ml ofDowfax 2A1 (product of Dow Chemical) into 3,000 ml of deionized water.Typically, coated substrate is immersed into the boiling Dowfax solutionfor 15 minutes. The coated substrate is then rinsed and cooled indeionized water, dried, and then tested and rated for blush and adhesionas described previously.

G. Solvent Resistance Test

The extent of “cure” or crosslinking of a coating is measured as aresistance to solvents such as methyl ethyl ketone (MEK). This test isperformed as described in ASTM D 5402-93. The number of double rubs(i.e., one back-and-forth motion) is reported. Preferably, the MEKsolvent resistance is at least 30 double rubs. H. Feathering Test

To test feathering, a suitably sized tab (e.g., of a similar size to asoda can opening) is scored on the backside of a coated metal panel,with the coated side of the panel facing downward. The test piece isthen immersed in a deionized water bath for 45 minutes at 85° C. Afterpasteurization, pliers are used to bend the cut tab to a 90-degree angleaway from the coated side of the substrate. The test piece is thenplaced on a flat surface, coated side down. The cut tab is gripped usingpliers and the tab is pulled from the test panel at an angle of 180degrees until it is completely removed to create an opening. Afterremoving the tab, any coating that extends into the opening on the testpanel is measured. The largest distance that the coating extends intothe opening is measured (feathering) and reported in inches. Coatingsfor easy-open food or beverage can ends preferably show feathering below0.2 inches (0.508 cm), more preferably below 0.1 inches (0.254 cm), mostpreferably below 0.05 inches (0.127 cm), and optimally 0.02 inches orlower (0.051 cm). Preferred beverage can end coatings of the presentdisclosure exhibit feathering properties pursuant to the values providedabove.

EXAMPLES

The disclosure is illustrated by the following examples. It is to beunderstood that the particular examples, materials, amounts, andprocedures are to be interpreted broadly in accordance with the scopeand spirit of the disclosures as set forth herein. Unless otherwiseindicated, all parts and percentages are by weight and all molecularweights are weight average molecular weight. Unless otherwise specified,all chemicals used are commercially available from, for example,Sigma-Aldrich, St. Louis, Mo.

Example 1: Preparation of a Functionalized Polymer

24.3 grams (“g”) Cylohexane-1,4-dimethanol (dissolved 90% by weight inwater), 101.8 g 2-Methylpropane-1,3-diol, 1.64 g1,1,1-Trimethylolpropane, 45.4 g isophthalic acid, 135.3 g terephthalicacid, and 0.36 g of a Tin-based catalyst were charged to a 4-neck,2-liter glass flask fitted with an electric heating mantle, a mechanicaloverhead stirrer, a thermocouple, a packed column (with a Dean-Starktrap and water-cooled condenser), and a stopper in the remaining neck. Aflow of nitrogen gas and an agitation rate of 100-200 revolutions perminute (“rpm”) were maintained throughout the process. The contents ofthe flask were slowly heated to 235° C. such that the head temperatureat the top of the packed column was maintained at, or below, 100° C.,and the water of reaction was collected in the trap and removed. Oncethe head temperature dropped below 80° C. and the acid number droppedbelow 10 mg KOH/g resin, the reaction was cooled to 180° C. 29.8 gSebacic acid and 16.2 g of ethylene glycol were then added to the flask,and the temperature was returned to 235° C. while maintaining a headtemperature below 100° C. and collecting the reaction water. Once thehead temperature dropped below 80° C., the batch temperature was reducedagain to 170° C. 28.5 g Maleic anhydride was added to the flask, and thetemperature was held at 170° C. for 1 hour. After this hold, 21.3 gXylene was added to the batch, the packed column was removed and thetrap was prepared for azeotropic distillation. The batch was adjusted to195-205° C. and reaction water collected until the acid number droppedbelow 10 mg KOH/g resin and the viscosity of a resin sample (cut to 50%non-volatile material (“NVM”) in additional xylene) was U—W(Gardner-Holt bubble tube scale). Once the resin was in the correct acidnumber and viscosity ranges, the batch was cooled to 180° C., and 13.4 gsorbic acid was added to the flask, and the 180° C. temperature wasmaintained for 5 hours. Following the hold, the temperature of the batchwas allowed to drop while 121.1 g Diethylene glycol monoethyl ether and51.8 g n-Butanol were added slowly to yield a 65% NVM resin solution

Example 2: Preparation of Functionalized Polymers Using Solvent-lessPolymerization Processes

The below Runs of Example 2 are prophetic examples that are intended toillustrate the production of polyester polymers using a representativesolvent-less polymerization process. The polymers resulting from Runs1-8 are high molecular weight polymers having a Mn between about 10,000and about 30,000 Daltons.

Run 1

A co-polyester is prepared having a target composition of 75 mol %dimethyl terephthalate residues, 25 mol % maleic anhydride residues, and100 mol % 1,4-cyclohexanedimethanol residues (CHDM), wherein theaforementioned mol %'s are relative to total moles of acid and acidequivalent reactants and total mole of glycol reactants.

A mixture of 56.63 g of dimethyl terephthalate, 9.5 g of maleicanhydride, and 0.0419 g of dibutyl tin oxide are placed in a500-milliliter flask equipped with an inlet for nitrogen, a metalstirrer, and a short distillation column. The flask is placed in aWood's metal bath already heated to 210° C. The stirring speed is set to200 RPM throughout the experiment. The contents of the flask are heatedat 210° C. for 5 minutes and then the temperature is gradually increasedto 290° C. over 30 minutes. The reaction mixture is held at 290° C. for60 minutes and then vacuum is gradually applied over the next 5 minutesuntil the pressure inside the flask reaches 100 mm of Hg. The pressureinside the flask is further reduced to 0.3 mm of Hg over the next 5minutes. A pressure of 0.3 mm of Hg is maintained for a total time of 90minutes to remove excess un-reacted diols. A high melt viscosity,visually clear and colorless polymer is obtained. This polymer has anexpected inherent viscosity (IV) of 0.56 deciliters per gram (“dl/g”).

Run 2

A co-polyester is prepared using the materials and methods of Run 1,except the glycol mixture is 50 mol % CHDM and 50 mol % tricyclodecanedimethanol (“TCDM”) and the final has an expected IV of 0.75.

Run 3

A co-polyester is prepared using the materials and methods of Run 1,except the glycol mixture is 33 mol % CHDM, 33 mol % TCDM Alcohol and 33mol % Methyl Propanediol and the final polymer has an expected IV of0.76.

Run 4

A co-polyester is prepared using the materials and methods of Run 1,except the glycol mixture is 33 mol % CHDM, 33 mol % 1,3 TetramethylCyclobutane Diol and 33 mol % Methyl Propanediol and the final polymerhas an expected IV of 0.67.

Run 5

A co-polyester is prepared using the materials and methods of Run 1,except the glycol mixture is 50 mol % CHDM and 50 mol % 1,3 TetramethylCyclobutane Diol and the final polymer has an expected IV of 0.69.

Run 6

A co-polyester is prepared using the materials and methods of Run 1,except the glycol mixture is 50 mol % TCDM and 50 mol % 1,3 TetramethylCyclobutane Diol and the final polymer has an expected IV of 0.89.

In order to introduce pendant functional groups, the polyester polymersof Runs 1 to 6 are reacted with an unsaturated compound having at leastone salt or salt-forming group (e.g., sorbic acid) using the processoutlined above in Example 1. The level of fictionalization may becontrolled by restricting the amount of the unsaturated compound havingat least one salt or salt-forming group to only the amount offunctionalization desired.

Run 7

The polyester polymer of Run 7 is made similar to the polymer describedin Run 1. In Run 7, however, rather than discharging immediately afterpolymerization, the polymer melt is cooled to about 180° C. This is theminimum temperature at which the polymer melt can be satisfactorilyhandled due to its increased viscosity at lower temperature. Once thepolymer reaches this temperature, 5.0 g (0.045 moles) of sorbic acid areadded to the reaction vessel. The reaction vessel is maintained at thistemperature to complete the Diels-Alder reaction between the polymer andthe sorbic acid. After this holding time NMR, FT-IR and titration dataare expected to indicate that 95% of the sorbic acid is bound to thebackbone of the base polymer

A high melt viscosity, visually clear and colorless polymer is obtained.This polymer has an expected IV of 0.56 dl/g.

Run 8

Run 8 is similar Run 7 except that 10.0 g (0.090 moles) of sorbic acidare added to the reactor. Analysis is expected to show that 97% of thesorbic acid is reacted.

The above Runs 1-8 of Example 2 illustrate that a solvent-free, meltpolymerized reaction scheme may be used in some embodiments to producefunctionalize polymers of the present disclosure.

The functionalized polyester polymers of Runs 1-8 may be neutralizedwith a suitable neutralizing agent such as a tertiary amine or ammoniaand can form a stable dispersion in an aqueous carrier or a combinedwater and solvent carrier and can be further formulated as describedherein.

Example 3: Preparation of Aqueous Dispersion Including theFunctionalized Polymer

The resulting solution from Example 1 was cooled to 80° C., and 26.0 gof an epoxy-functional acrylic resin was added (the epoxy-functionalacrylic resin contained Glycidyl methacrylate, Styrene, and Methylmethacrylate, has an Mn of approximately 5,000 Daltons, and is cut to51.5% NVM in organic solvent). Maintaining 80° C., 7.16 gDimethylethanolamine were added and the resin was stirred for 5 minutes.After the 5-minute hold, 375.9 g deionized water was added to the flaskover 60 minutes.

Example 4: Model Reaction to Determine Ratio of Ene and Diels-AlderReaction Products

Because it would be extremely difficult to determine the reactionmechanisms occurring in a complex maleated polyester when reacted withsorbic acid (as in Example 1), a model reaction was performed. To a 500ml 4-neck flask equipped with an electric overhead mixing device, watercooled condenser, nitrogen inlet, and thermocouple connected to atemperature controlling device with heating mantle was added 200 partsdiethyl maleate (acting as the unsaturated polyester mimic) and 78.5parts sorbic acid. These amounts mimic the ratio of moles of sorbic acidto moles of maleic anhydride in Example 1 (0.6 to 1). Mixing wascommenced at 200 rpm's and the material was heated to 180° C. over thecourse of 30 minutes. The material was held at 180° C. for 5 hours, atwhich time the material was cooled to room temperature and discharged.Using a Liquid Chromatography/Mass Spectroscopy Instrument, severalreaction products were detected, all having a mass of 284.126. Byanalyzing the mass spectroscopic fragmentation patterns of each reactionproduct, it could be determined which product was the result of an Enereaction, and which was the result of a Diels-Alder reaction. It wasshown to be 75% Ene reaction, 25% Diels-Alder reaction. When the samereaction was run between diethyl maleate and crotonic acid (3-methylacrylic acid), no reaction was observed under the test conditions. Whenthe same reaction was run between diethyl maleate and vinyl acetic acid,an Ene reaction product was observed. Crotonic acid and vinyl acetic areincapable of undergoing a Diels-Alder reaction with diethyl maleate.

Example 5: Preparation of Coating Compositions

A clear interior beverage end lining was prepared with the followingsolids composition: 92.4% (by weight) of the polyester/acrylic resindispersion from Example 3; 2.5% of a methylol functional phenolformaldehyde resin; 5% of a mixed ether melamine formaldehydecrosslinking resin; 0.1% of an amine blocked Dodecyl benzene sulfonicacid catalyst; and 1% of a carnauba lubricant in emulsion form. Thefinal coating composition was adjusted to 33.5% NVM, of which thenon-volatile component was approximately 54% water and 46% organicsolvents.

Example 6: Coated Substrate

The coating composition of Example 5 was applied at a dry film weight of6.5 to 7.5 milligrams per square inch to pretreated aluminum coil in acoil coating application. The coated coil had a 10-second dwell time ina heated oven to achieve a 465° F./241° C. peak metal temperature. Thecoating properties of the cured coating were assessed using varioustests. The data from these tests is summarized in the below Table 1. Thedata of Table 1 indicates that the cured coating composition exhibits adesirable balance of coating properties for use as a coating for ariveted beverage can end. The cured coating also exhibited very goodfeathering resistance.

TABLE 1 MEK Solvent Double Rubs 49 Water Pasteurization (45 minutes at66° C.) Blush 10 Adhesion 10 Water Retort (90 minutes at 121° C.) Blush9/9 Adhesion 10/10 Fabrication Test 202 Converted End Milliamps(initial) 0.2 mA 202 Converted End Milliamps (after 0.6 mA Dowfax)Coefficient of Friction (Thwing Albert) 0.069

The complete disclosure of all patents, patent applications, andpublications, and electronically available material cited herein areincorporated by reference. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. The disclosureis not limited to the exact details shown and described, for variationsobvious to one skilled in the art will be included within the disclosuredefined by the claims. The disclosure illustratively disclosed hereinsuitably may be practiced, in some embodiments, in the absence of anyelement which is not specifically disclosed herein.

What is claimed is: 1-20. (canceled)
 21. A method of making afunctionalized polymer comprising: providing an unsaturated precursorpolymer having a number average molecular weight of at least 2,000 andone or more double or triple bonds; and reacting in a Diels-Alderreaction, an Ene reaction, or a combination thereof: (i) an unsaturatedcompound having one or more functional groups with (ii) the unsaturatedprecursor polymer such that a covalent attachment is formed between theunsaturated compound and the unsaturated precursor polymer.
 22. Themethod of claim 21, wherein the unsaturated precursor polymer is alinear or substantially linear polymer.
 23. The method of claim 21,wherein the polymer includes a plurality of functional-group-containingside groups formed from the unsaturated compound, and wherein at leastone side group was attached via a Diels-Alder reaction and at least oneside group was attached via an Ene reaction.
 24. The method of claim 21,wherein the precursor polymer comprises a polyester polymer, and whereinthe one or more double or triple bonds of the unsaturated polymer isprovided by one of an unsaturated diacid, an unsaturated anhydride, oran unsaturated diol reacted into a backbone of the unsaturated precursorpolymer.
 25. The method of claim 21, wherein the one or more functionalgroup comprises an active hydrogen group, an isocyanate group, a blockedisocyanate group, a ketone group, or a mixture thereof.
 26. The methodof claim 21, wherein the one or more functional group comprises a saltor salt-forming group.
 27. The method of claim 21, wherein the double ortriple bonds of the unsaturated precursor polymer are one or morecarbon-carbon double bonds and the unsaturated compound includes atleast one carbon-carbon double bond.
 28. The method of claim 27, whereinone or both of the unsaturated precursor polymer and the unsaturatedcompound include conjugated carbon-carbon double bonds.
 29. The methodof claim 21, further comprising forming an aqueous coating compositionincluding the resulting functionalized polymer.
 30. The aqueous coatingcomposition resulting from the method of claim
 29. 31. The coatingcomposition of claim 30, wherein the coating composition is suitable foruse in forming a food-contact coating, and wherein the coatingcomposition includes at least 50 weight percent of the polymer based ontotal resin solids.
 32. The functionalized polymer resulting from themethod of claim
 21. 33. A method of making a functionalized polyesterpolymer comprising: providing an unsaturated precursor polyester polymerhaving one or more double or triple bonds; and reacting in a Diels-Alderreaction, an Ene reaction, or a combination thereof: (i) an unsaturatedcompound having one or more functional groups with (ii) the unsaturatedprecursor polyester polymer such that a covalent attachment is formedbetween the unsaturated compound and the unsaturated precursor polyesterpolymer; wherein the one or more functional group comprises an activehydrogen group, an isocyanate group, a blocked isocyanate group, aketone group, or a mixture thereof.
 34. The method of claim 33, whereinthe unsaturated precursor polyester polymer has a number averagemolecular weight of at least 4,000.
 35. The method of claim 33, whereinone or both of the unsaturated precursor polyester polymer and theunsaturated compound include conjugated carbon-carbon double bonds. 36.The method of claim 33, wherein the unsaturated compound comprisessorbic acid or neutralized sorbic acid.
 37. The method of claim 33,wherein the functionalized polyester polymer resulting from the methodhas a glass transition temperature of at least 25° C.
 38. The method ofclaim 37, wherein the functionalized polyester polymer resulting fromthe method comprises a water-dispersible polymer.
 39. The method ofclaim 33, wherein the functionalized polyester polymer resulting fromthe method includes a plurality of the side groups and at least one ofthe side groups is a Diels-Alder reaction product and at least one ofthe side groups is an Ene reaction product.
 40. The functionalizedpolyester polymer resulting from the method of claim 39.